Biomedical subjects

M S Shahriar

Publications and source records attributed to M S Shahriar.

8 recordsLinked to original sources

PubMed2006

Shift-invariant real-time edge-enhanced VanderLugt correlator using video-rate compatible photorefractive polymer.

We demonstrated a real-time shift-invariant VanderLugt correlator (VLC). The VLC was implemented with a 37 microm thick bis-triarylamine side-chain polymer matrix photorefractive (PR) polymer composite operating at 532 nm wavelength. Correlation selectivity was enhanced by real-time edge enhancement. The advantage of the VLC is that its architecture allows overcoming the PR material response speed. A correlator of this type enables a fast shift-invariant search of a large optical image database. A high degree of shift invariance in our correlator was possible because of the material thickness. The angular bandwidth of this material was measured experimentally in a degenerate four-wave mixing setup, and it was found to be in a very good agreement with the theory.

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PubMed2005

Demonstration of a multiwave coherent holographic beam combiner in a polymeric substrate.

We demonstrate an efficient coherent holographic beam combiner (CHBC) that uses angle multiplexing of gratings in a thick polymeric substrate. Our experimental results compare well with the theoretical model based on the coupled-wave theory of multiwave mixing in a passive medium. A CHBC of this type may prove useful in producing a high-power laser by combining amplified beams produced by splitting a master oscillator. Furthermore, the ability to angle multiplex a large number of beams enables a CHBC to be used in multiple-beam interferometry applications as a high-precision surface sensor.

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PubMed2004

Demonstration of a simple technique for determining the M/# of a holographic substrate by use of a single exposure.

We propose and demonstrate a simple technique for determining the M/# parameter of a holographic recording material. In this method, divergent object and reference beams are used to produce a spatially varying index modulation. One can analyze the resultant diffraction pattern to find M/# by using only a single grating; existing techniques require many gratings.

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PubMed2004

Ultrafast holographic Stokesmeter for polarization imaging in real time.

We propose an ultrafast holographic Stokesmeter using a volume holographic substrate with two sets of two orthogonal gratings to identify all four Stokes parameters of the input beam. We derive the Mueller matrix of the proposed architecture and determine the constraints necessary for reconstructing the complete Stokes vector. The speed of this device is determined primarily by the channel spectral bandwidth (typically 100 GHz), corresponding to a few picoseconds.

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PubMed2004

Polarization of holographic grating diffraction. II. Experiment.

The transmittance, ellipsometric parameters, and depolarization of transmission, diffraction, and reflection of two volume holographic gratings (VHGs) are measured at a wavelength of 632.8 nm. The measured data are in good agreement with the theoretical simulated results, which demonstrated the correlation between the diffraction strength and the polarization properties of a VHG. Vector electromagnetic theory and polarization characterization are necessary for complete interpretation of the diffraction property of a VHG. The diffraction efficiency is measured at 532 nm in a polarization-sensing experiment. The measured data and theoretical simulation have demonstrated the potential application of the holographic beam splitter for polarization-sensor technology.

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PubMed2003

Superparallel holographic correlator for ultrafast database searches.

We describe a superparallel holographic optical correlator that performs two-dimensional spatial and angular multiplexing simultaneously. The key step in this architecture is the use of a holographic multiplexer to split a query image into many copies before it applies them to the holographic database. A holographic demultiplexer, in conjunction with an aperture, is used to identify the location and the angle of the brightest correlation peak. This architecture uses only O(square root of N) detector elements to search through N unsorted images in a single query. We demonstrate the basic features of this architecture, using three spatial locations with eight angle-multiplexed images in each location.

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PubMed2001

Observation of ultraslow and stored light pulses in a solid.

We report ultraslow group velocities of light in an optically dense crystal of Pr doped Y2SiO5. Light speeds as slow as 45 m/s were observed, corresponding to a group delay of 66 micros. Deceleration and "stopping" or trapping of the light pulse was also observed. These reductions of the group velocity are accomplished by using a sharp spectral feature in absorption and dispersion that is produced by resonance Raman excitation of a ground-state spin coherence.

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PubMed2001

Long distance, unconditional teleportation of atomic states via complete Bell state measurements.

We propose a scheme for creating and storing quantum entanglement over long distances. Optical cavities that store this long-distance entanglement in atoms could then function as nodes of a quantum network, in which quantum information is teleported from cavity to cavity. The teleportation is conducted unconditionally via measurements of all four Bell states, using a novel method of sequential elimination.

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